Cohen, D. (1994). Precalculus with unit-circle trigonometry (2nd ed.). West Publishing Company.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रCohen, David. Precalculus with Unit-circle Trigonometry. 2nd ed. Minneapolis, NY: West Publishing Company, 1994.
एमएलए (9वां संस्करण) प्रशस्ति पत्रCohen, David. Precalculus with Unit-circle Trigonometry. 2nd ed. West Publishing Company, 1994.
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